The growth and production of adult mosquitoes from aquatic, heterotrophic, larval habitats is the primary determinant of adult presence and density, and strongly influences vectorial capacity, but it is constrained by conversion of refractile organic material into ingestible and digestible microbial biomass. The tree hole habitat of several mosquito species is our model system to study this phenomenon. Our long term goals are to quantify the biological basis for and constraints on mosquito production, to identify the efficiency of utilization of these resources, to elaborate a realistic model of larval growth, and to genetically transform bacteria in larval habitats to produce anti-larval toxins. Research approaches across 3 specific aims include a functionally axenic (germ-free) experimental system into which individual food sources including microorganisms can be provisioned; the utilization of stable isotope analyses (13C/12C; 15N/14N) to track larval foods to their sources; and molecular characterization and manipulation of the microbial community. Growth enhancing effects of microbial metabolism, and inhibiting effects of humic substances, will be analyzed. A reaction norm concept is proposed in which developmental time to and mass at metamorphosis (pupation) are postulated to be flexible life history traits nutritionally constrained into a pupation window. A growth model is elaborated herein, in which food conversion efficiencies are elaborated, thus we will iteratively test growth responses to food sources of various qualities. Four mosquitoes species sharing the same larval habitat and resources (Ochlerotatus triseriatus, Ochlerotatus japonicus, Aedes albopictus, and t Culex pipiens, all vectors of human pathogens) will be compared to assess growth rates under conditions of intense intra- and interspecific competition, both to make predictions of competitive outcomes and potential for ecological displacement, and to quantify comparative efficiency of utilization of larval foods.The role of the microbial community (bacteria, fungi, and protozoans) will be assessed through microbial biomass and growth measures, the use of functional gene arrays, and with estimates of polymer degradation enzymes, including xylanases, cellulases, chitinases. Manipulation of the Flavobacterium component of the microbial community with molecular genetic tools to express proteins and genes of interest will be conducted, including microbial toxin genes and synergistic chitinases.